The 3GPP (3rd Generation Partnership Project) launched LTE (Long Term Evolution) in 2005, which aims to provide support for increasing requirements from operators and subscribers with higher data throughput and better network performance.
MBMS (Multimedia Broadcast/Multicast Service) is introduced in 3GPP Rel. 6 as a one-to-more point service that transmits data from a single data source to multiple subscribers so as to share network (including core network and access network) resources and provide services for more multimedia subscribers having identical requirements with fewer resources. In a wireless access network, MBMS service can, by using public transmission channel and public wireless bearer, implement both pure-text, lower-rate multicast and broadcast of message type and higher-rate multicast and broadcast of multimedia services, such as mobile TV phone.
Currently, 3GPP has devised respective pilot signal mapping methods for unicast service and broadcast/multicast service with a single antenna, i.e., methods for transmitting pilot signals via a single antenna.
LTE recommends support for enhanced MBMS service (E-MBMS). E-MBMS can share carriers with unicast service, and can also use a separate carrier, i.e., separate large cell coverage mode. The compact integration of unicast and MBMS services is able to provide subscribers with services in a more efficient way.
In the existing protocols, pilot signals related to E-MBMS are mapped with respect to a single transmit antenna. In a TDM (Time Division Multiplexing) case of E-MBMS and unicast services, two types of pilot signals are placed within an E-MBMS subframe, one type is used for E-MBMS channel estimation, and the other type is used for unicast service pilot symbols for controlling channel decoding. At present, pilot templates are each designed on the basis of a single transmit antenna situation taking into account of the mixing co-existence of unicast service and E-MBMS, i.e., the two types of services are time division multiplexed at a subframe level. Pilot signal mapping based on multi-transmit-antenna, however, has not been considered in the TDM case of E-MBMS and unicast services.
There is yet no proposal about how to set pilot signals in an E-MBMS subframe and map them to transmit antennas when there is more than one transmit antennas so that at a reception side respective channel estimations can be performed for both of E-MBMS and unicast services based on the received pilot signals.